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  437 
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  LI. 
  Proceedings 
  of 
  Learned 
  Societies. 
  

  

  GEOLOGICAL 
  SOCIETY. 
  

  

  [Continued 
  from 
  vol. 
  xvii. 
  p. 
  772.] 
  

  

  February 
  10th, 
  1909.— 
  Prof. 
  W. 
  J. 
  SoUas, 
  LL.D., 
  Sc.D., 
  P.R.S., 
  

   President, 
  in 
  the 
  Chair. 
  

  

  npHE 
  following 
  communications 
  were 
  read 
  : 
  — 
  

  

  1. 
  ' 
  Note 
  on 
  eome 
  Geological 
  Features 
  observable 
  at 
  the 
  Carpalla 
  

   China-Clay 
  Pit 
  in 
  the 
  Parish 
  of 
  St. 
  Stephen's 
  (Cornwall).' 
  By 
  

   Joseph 
  Henry 
  Collins, 
  F.G.S. 
  

  

  An 
  east-and-west 
  fault 
  traverses 
  this 
  pit 
  near 
  its 
  southern 
  wall, 
  

   with 
  a 
  downthrow 
  to 
  the 
  south 
  of 
  more 
  than 
  50 
  feet. 
  North 
  of 
  the 
  

   fault 
  there 
  is 
  china-clay 
  rock 
  or 
  ' 
  carclazyte,' 
  at 
  one 
  point 
  underlying 
  

   granite 
  not 
  sufficiently 
  altered 
  to 
  yield 
  china-clay, 
  and 
  sometimes 
  

   containing 
  embedded 
  leuticles 
  or 
  irregular 
  masses 
  of 
  partly-kaolinized 
  

   granite. 
  The 
  carclazyte 
  is 
  often 
  traversed 
  by 
  veins 
  of 
  secondary 
  

   quartz, 
  in 
  most 
  instances 
  associated 
  with 
  schorl. 
  It 
  also 
  contains 
  

   lepidotite, 
  gilbertite, 
  topaz, 
  fluor, 
  and 
  schorl. 
  South 
  of 
  the 
  fault 
  

   there 
  is 
  nearly 
  horizontal 
  tourmaline-schist, 
  at 
  one 
  point 
  50 
  feet 
  

   thick, 
  and 
  thinning 
  off 
  southwards 
  and 
  eastwards. 
  This, 
  like 
  the 
  rock 
  

   of 
  the 
  north 
  side, 
  is 
  overlain 
  by 
  subsoil 
  or 
  ' 
  growan,' 
  covered 
  in 
  turn 
  

   by 
  soil 
  or 
  ' 
  meat-earth.' 
  Underlying 
  the 
  schist 
  there 
  occurs 
  also 
  

   china-clay 
  rock 
  to 
  a 
  distance 
  of 
  many 
  fathoms 
  from 
  the 
  fault. 
  

   This 
  occurrence 
  of 
  china-clay 
  under 
  a 
  thick 
  schistose 
  overburden 
  

   is 
  unique 
  in 
  Cornwall, 
  although 
  the 
  other 
  features 
  of 
  the 
  pit 
  are 
  

   reproduced 
  elsewhere. 
  The 
  author 
  considers 
  that 
  this 
  example 
  is 
  

   strongly 
  in 
  favour 
  of 
  the 
  pneumatolytic 
  origin 
  of 
  carclazyte, 
  the 
  

   gases 
  producing 
  the 
  change 
  being 
  possibly 
  in 
  part 
  carbonic 
  acid, 
  

   but 
  probably 
  to 
  a 
  more 
  important 
  degree 
  chlorine, 
  fluorine, 
  and 
  

   boron. 
  

  

  2. 
  ' 
  Some 
  Recent 
  Observations 
  on 
  the 
  Brighton 
  Cliff-Formation.' 
  

   By 
  Edward 
  Alfred 
  Martin, 
  F.G.S. 
  

  

  The 
  author 
  records 
  in 
  his 
  paper 
  certain 
  features 
  presented 
  by 
  

   the 
  face 
  of 
  the 
  cliffs 
  between 
  successive 
  falls 
  at 
  Black 
  Hock, 
  Brighton, 
  

   during 
  the 
  past 
  eighteen 
  years. 
  As 
  the 
  cliffs 
  have 
  worn 
  back, 
  the 
  

   base-platform 
  of 
  Chalk 
  grows 
  in 
  height, 
  and 
  the 
  layer 
  of 
  sand 
  

   which 
  Prestwich 
  found 
  above 
  the 
  Chalk 
  grew 
  thinner 
  and 
  thinner 
  

   until 
  finally 
  it 
  completely 
  disappeared. 
  At 
  the 
  same 
  time, 
  the 
  

  

  Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  105. 
  Sept. 
  J 
  909. 
  2 
  G 
  

  

  